Re: Would my postgresql 8.4.12 profit from doubling RAM?

On 08/30/2012 07:42 PM, Alexander Farber wrote:
> Hello,
>
> I run CentOS 6.3 server with 16 GB RAM and:
>      postgresql-8.4.12-1.el6_2.x86_64
>      pgbouncer-1.3.4-1.rhel6.x86_64
>
> The modified params in postgresql.conf are:
>      max_connections = 100
>      shared_buffers = 4096MB
>
> and the pgbouncer runs with:
>      pool_mode = session
>      server_reset_query = DISCARD ALL;
>
> The main app is a card game with 30-500
> simultaneous users for which I save some
> playing stats into the db +
> PHP scripts to display those stats again.
>
> I have an option to double the RAM for EUR 180,-
> but wonder if it will improve any performance and
> also what to do on the PostgreSQL side once
> I've doubled the RAM (like double shared_buffers?
> but how do I find out if it's needed, maybe they're empty?)
>
> Below is a typical top output, the pref.pl is my game daemon

What you really want to look at is the iowait%, which you aren't
showing, and at vmstat output to see what kind of disk read rates you're
doing.

Looking at `free -m` can be informative too; if your server has more
than a few hundred MB of free memory there's unlikely to be much to gain
by adding more RAM 'cos it can't find anything useful to do with what it
already has. In practice this is rare.